The present invention relates to a method for coating a surface of a continuous web having a first surface and a second surface with a coating powder. The method comprises: Allowing the web to move between electrodes which are in different potentials, applying the coating powder on the surface of the web by utilizing the difference in the electric potential, and finishing the coated surface of the web.
It is possible to treat the web by the dry surface treatment process by using a charging electrode and an earthing electrode on the opposite sides of the web. This principle is disclosed for example in EP 0982120, WO 98/11999 and Fl 105052 which corresponds to WO 00/03092 and EP 1099023.
If a double-sided treatment is required, the problem with treating only one side of the web at a time is that the coating powder has to be applied on the first surface of the web, and after that the first surface is finished for example by using heat and pressure. In the next process step, the same procedure is repeated to treat the second surface of the web.